1. Field of the Invention
The present invention relates to a storage battery module formed by joining together a plurality of secondary batteries into a module.
2. Description of Related Art
In recent years, a lithium secondary battery has been used as a battery for a power source of a mobile electronic device such as a cellular phone, a notebook-sized personal computer, or the like since it has a high energy density and can achieve size and weight reduction. Furthermore, a lithium secondary battery has been coming into focus also as a motor driving power source of an electric vehicle (EV), a hybrid electric vehicle (HEV), or the like or as a storage battery for power storage since it can achieve a larger capacity.
A lithium secondary battery as described above has the following configuration. That is, an electrode group in which a positive electrode plate and a negative electrode plate are disposed opposite to each other with a separator interposed therebetween is housed inside an outer case constituting a battery can, and an electrolyte is filled therein. The lithium secondary battery is provided with a positive electrode current collector terminal that is connected to a positive electrode current collector tab of each of a plurality of the positive electrode plates, a positive electrode external terminal that is electrically connected to the positive electrode current collector terminal, a negative electrode current collector terminal that is connected to a negative electrode current collector tab of each of a plurality of the negative electrode plates, and a negative electrode external terminal that is electrically connected to the negative electrode current collector terminal.
Furthermore, it has been sought to join together a plurality of such lithium secondary batteries to use them as a large-scale power source for providing power, and there has already been proposed, for example, a battery assembly formed by stacking one on top of each other, single cells each constituted by a secondary battery including a stacked type electrode group (see, for example, Patent Document 1: JP-A-2003-288883).
A lithium secondary battery including a stacked type electrode group has the following configuration. That is, an electrode group in which positive electrode plates and negative electrode plates are stacked via separators to form a plurality of layers is housed in an outer case, and a non-aqueous electrolyte is filled therein. The lithium secondary battery is provided with a positive electrode current collector terminal that is connected to a positive electrode current collector tab of each of the positive electrode plates, an external terminal that is electrically connected to the positive electrode current collector terminal, a negative electrode current collector terminal that is connected to a negative electrode current collector tab of each of the negative electrode plates, and an external terminal that is electrically connected to the negative electrode current collector terminal.
By joining together a plurality of lithium secondary batteries having this configuration, a large capacity battery assembly (storage battery module) can be constructed. Furthermore, as a method for connecting together a plurality of secondary batteries, preferably, a predetermined number of secondary batteries are integrally connected together, with a protection circuit also integrally incorporated therewith, to form a base module having a predetermined capacity and made up of the predetermined number of secondary batteries, and the base modules are combined to form a storage battery that achieves a predetermined electricity storage capacity.
Furthermore, in joining together a plurality of secondary batteries, preferably, the secondary batteries can be securely fixed so that a relative positional shift therebetween is prevented, and an operation of interconnecting external terminals to be connected to each other is facilitated. From this viewpoint, there has already been proposed a battery pack in which a plurality of battery cells are integrally assembled, and electrode terminals of adjacent ones thereof can be easily interconnected without the use of a bus bar (see, for example, Patent Document 2: JP-A-2008-181765).
A storage battery module having a predetermined battery capacity can be manufactured by electrically connecting together a plurality of secondary batteries, and a large capacity storage battery can be constructed by combining a plurality of such storage battery modules. In assembling a plurality of secondary batteries, however, in the configuration in which stacked type secondary batteries having a rectangular shape in a plan view are simply stacked, the secondary batteries are brought into contact with each other at their center portions where heat is generated, which brings about an undesirable situation in which temperature non-uniformity occurs to cause electrode deterioration.
Locally caused electrode deterioration is undesirable in that it leads not only to a decrease in battery capacity but also to a short circuit due to electrode peeling or a short circuit due to a dendrite generated when an electrolyte is partly dried. Furthermore, in each of final products such as a power storage module and a battery assembly, preferably, for electrical connection to an external device, two terminals of the storage battery module, which are a positive electrode terminal and a negative electrode terminal, are provided close to each other.
Based on the above, in constructing a storage battery module having a predetermined capacity by joining together a plurality of stacked type secondary batteries, preferably, the module is configured such that the plurality of secondary batteries can be compactly connected together while non-uniformity in battery temperature distribution is prevented, and wiring connection work is facilitated. Furthermore, preferably, the module is configured such that positive and negative electrode input/output external terminals are provided close to each other.